AbstractAcetylcholinesterase (AChE) was extracted from normal and dystrophic C57BL/6J mouse hindlimb muscles and its molecular forms fractionated by sucrose density gradient ultracentrifugation. In the soleus muscles from 6‐ to 7‐week‐old mice an increase in the 3 Svedberg unit (S) and a decrease in the 16S AChE molecular forms was observed in dystrophic animals compared to controls. At 12–13 weeks of age, no major significant differences in the relative proportions of AChE molecular forms were noted. In the extensor digiorum longus (EDL) muscles of 6‐ to 7‐week‐old dystrophic mice a significant decrease in the proportion of the 10S AChE molecular form and an increase in the 3S and 5S forms was observed. At 12–13 weeks, the dystrophic EDL muscles again displayed a decrease in the 10S form; however, the increase in the 3S and 5S AChE forms, while still apparent, was not significant. These results provide evidence for a biochemical abnormality in the distribution of specific AChE molecular forms, and a differential expression of this abnormality in the soleus